Plastic bags made of polyethylene, PVC or other commonly used plastic or thermoplastic materials enjoy widespread use for the containment of trash and other waste. They are also widely used for storage and for carrying groceries and other items. Their low cost, strength, extreme light weight, ease of folding and imperviousness to water and other liquids makes them ideal for these purposes.
Plastic bags have no structural rigidity of their own. In use, therefore, especially for the containment of trash and other waste, they are ordinarily fitted within a can or container. Plastic bags are made in many standard sizes and, therefore, can be selected for closest fit with the desired container. A plastic bag is usually held within the container by lapping its open end over the rim of the container and tugging it downwardly. They are in this way frictionally fitted to the top of the container, but not to its bottom.
Plastic bags packaged for retail sale as container liners are usually joined end to end in a single continuous roll, with the liners being separated by perforated lines. These rolls are placed in paper or similar disposable cartons or boxes and extracted for use one at a time, for example, through a slot in the container. Their inherent slipperiness and flatness make it difficult to package them for sale in other ways, as by stacking them. Upon extraction from the container, they are separated from each other by pulling them apart along the perforated or serrated line.
Manufacturers strive to make plastic bags as thin as possible, in order to reduce the cost of materials and the weight of the bags themselves. Reducing the weight of each bag, however, makes a group of bags, if stacked, likely to topple over. Without special racks or other holders, therefore, it is not practical to stack folded plastic bags one atop another. The trade has developed a number of stacking arrangements and devices to remedy this, as for example, the "V" shaped stacking apparatus in U.S. Pat. No. 3,467,249 and the interlaced bag dispensing system of U.S. Pat. No. 3,392,825.
Extremely lightweight liner bags also tend to slip out of the container when it is turned on its side or upside down. Also, such thin plastic bags will break or tear at their bottoms when too great a loads placed in them.